Boosted solar water heaters can include a booster heater powered by electricity. A major advantage of solar water heaters is that they substantially reduce the requirement for mains electricity. It is desirable to reduce or minimize use of the booster heater. When heated water is drawn from the tank, an equal volume of unheated water is delivered to the tank from the water supply. If a large demand for hot water occurs when no solar input is available, or if the demand exceeds the rate of reheating available from the solar collector panels, the booster heater is used to replenish the heated water.
AU2005299246 describes a system and method for measuring the volume of hot water consumed by measuring the flow of water through the heater using a flow meter. To implement this, temperature sensors are fitted to the inlet and outlet of the tank, and a flow meter is required.
A flow meter is an added cost in the manufacture of a water heater. Flow meters have moving parts and require additional installation. Thus, this invention proposes a system for measuring the energy consumption which does not require the use of a flow meter to determine the volume of heated water consumed.